Process of making phosphate fertilizers.



S. B. NEWBERRY & H. N. BARRETT.

PROCESS OF MAKING PHOSPHATE FERTIL|ZERS..

APPLICATION FILED NOV. 4. 1912.

1,162,944. Patented Dec. 7, 19k").

invented a certain SPENCER B. 'NEWBERRY AND HARVEY N.

BARRETT, or BAYBRIDGE, oHIo.

PROCESS OF MAKING PHOSPHATE FERTILIZERS.

Appliciihn filed November 4, 1912. Serial N 6. 729,299.

To all whom it may concern:

Be it known that we, SPENCER B- NEW- BERRY and HARVEY N. BARRETT,citizens of the United States, residing at Baybridge, in the county ofErie new and useful Improvement in Processes of Making PhosphateFertilizers, of which the following is a specification. s.

This invention relates to improvements in the process of renderingnatural phosphates available for use as fertilizers.

The particular apparatus whereby the invention can be carried out isillustrated in the accompanying drawings, in which Figure 1 is a sideelevation of the kiln and Fig. 2 is a section on line 2-2 of Fig. 1.

The kiln A rests upon rollers B B and is revolved by gearingnot shown inthe drawing. It is heated internally by a flame or flames of coal-dust,oil or gas, blown in with air through G. The phosphate mixture isintroduced into the space I, in which, if wet, it is rapidly dried bythe hot gases and by contact with the hot lining. The dried mixturepasses down the kiln, being lifted and turned over by the shelves F F,and is kept from reaching too' high temperature by radiation of heatthrough the lining E. Between the drying zone I and the middle point ofthe kiln the mixture is exposed to moderate temperature, and from themiddle point to the lower end of the shelves it is subjected to thehighest heat. The calcined product is discharged through the hood H intothe cylinder C, in which it is (:(ioled by air drawn in by the draft ofthe st-ac In order that the process may be fully understood, we willdescribe it more or less in detail, and particularly set forth thosedetails of operation which, when closely followed, are likely to givethe best and most economical results, having reference to the process ofcalcination of I the addition of a small percentage of reagents, as forexample, alkalis or alkalimetal salts. These details of operation are asfollows:

1. The conversion to citrate-soluble con- Specification of LettersPatent.

and State of Ohio, have phosphates with Patented Dec. 7, 1915.

dition is brought about by exposure of the phosphate to sufficientlyprolonged and intimate contact with a rapid current of highly heatedgases. this intimate contact it is most important that the materialtreated shall be in a porous and cellular condition, in order that thegases may penetrate and envelop every particle or portion of thesubstance. This we accomplish by grinding the phosphate to a liquidslurry and introducing this slurry at the upper end of the revolvingkiln in which the calcining is effected.

We wish it to be understood that wedo not limit ourselves to theabove-described method of securing a porous cellular or laminatedcondition of the'phosphate mix-- ture, and that other devices ormanipulations by which free circulation of the hot gases through allparts of the material treated may be secured do not constitute adeparture from our forth.

2 If the phosphate in admixture with alkali-metal compounds is heatedwhile at rest or out of intimate contact with the hot gases, it tends tofuse together into compact grains or lumps, which in the further processof calcination are scarcely at all converted into citrate-soluble form.To avoid this injurious effect it is necessarythat thematerial duringthe whole course of the heating shall be actively agitated and turned Toproduce and maintainprocess as herein set over, thus thoroughlypromoting continued contact of the gases with every part of the chargeand preventing the formation of lumps which would escape further action.This agitation is effected by the revolution of the kiln and increasedby the lifting and rolling action of a number of shelves or ridges inthe kiln lining, which extend from the end of the drying zone nearly tothe point of discharge of the calcination product.

3. In the first stage of the heating the temperature of the chargeincreases rapidly, and under the combined action of heat, agitation andintimate contact with a rapid current of hot gases the alkali-metalcomof its acid or'other' volatile constituents.

This' action' takes place actively at a-temperature'of 2000 degrees F.or over, provided the material is porous and-the current of hot gases'siifliciently rapid. Under these conditions such alkali-metal compoundsfro ' andc'arbon'dioxid, leaving a residue of al-- as hydrate, sulfateor carbonate, which are scarcelyaffected by heating to muchhighertemperatur'es when at "rest, are rapidly decomposed withevolution, respectively, of -water, sulfur dioxid and oxygen,

kal-i-Inetal-oxidwhich We term residual alfkali. Thevolatileconstituents may be said to be blown out of the salts by contactwith the current of hot gases. It is probable that the residual alkalienters into com bination with the phosphate of lime,.forming analkali-lime phosphate which is again in large measure decomposed atthehigher temperature ofthe later-stage of the process, and that thiscombination and subsequent decomposition plays an important part in theconversion of the phosphate into citrate-soluble condition.

'perature of about 2400 degrees to 2600 degrees is required, and in thisstage, 'under the combined action'of heat, agitation and intimatecontact with a rapid. current of highly heated gases, the residualalkali is in turn and in large measure volatilized, and

simultaneously with the expulsion of alkali the percentage of. citratesol'uble phosphoricacid rapidly increases, until, with proper adjustmentof temperature and duration of,

- heating, the conversion to citrate-soluble conditionbecomespractically complete, only traces of insolublephosp'horic' acidremaining. The product of the operation conducted as above describedappears in the .form of brown or black masses or fragments,

. extremely porous and light, and so soft that it can be crushed topowder by pressure of the fingers. Dur1ng the entire courseof thecalcination the exp ulsion' of the volatile constituents 'of the alkalimetal compound and of the residual alkali tends to prevent ove r-heatingand-fusion of the material. This expulsion takes place normally andrapidly if- .the'material is exposed to and I penetrated by arapidly-moving current of -hot gases, for example sucha current as isproduced by. introducing the fuel at the lower end of the kiln inadmixture with a current of air under four or five ounces pressure andbymaintaining a strong draft in the stack at the, upper end of the kiln. 1Under these conditions the material remains 4. In the final stage ofcalcinat'iona te'min the finalstage of heating, and the phosphate isrendered practically completely citrate-soluble. On the other hand, ifthe current of hot gases is slow and sluggish or does not freelypenetrate the charge, little or no decomposition and expulsion of thealkali-metal salt takes place, the material fuses 0r sinters togetherinto impervious masses, and practically no conversion intocitrate-soluble condition is effected.

I An additional safeguard against the fusion or agglomeration of thematerial, especially in the earlier stage of heating, consistsin'carrying on the calcination in a kiln provided with a comparativelythin refractory lining, through which radiation of heat takes place to aconsiderable degree. The effect of this radiation is to keep theinterior of the kiln walls at a somewhat lower temperature than that ofthe charge or the gases passing .through the apparatus, and thus toprevent the charge from becoming over-heated and fusedby contact withthe hot lining. By alkali-metalcompound we mean any compound of thealkali-metals as potassium or sodium, with hydroxyl or the common acids,forexample the hydrate, carbonate,

chlorid, sulfate, bisulfate, nitrate, etc. We prefer to use sodiumsulfate or bisulfate, on account of the cheapness of these reagents andthe ease with which they undergo decomposition under the conditions ofcalci- -nation herein described. We find, however,

that any co'mpoundor' combination of the :alkali-metals substantiallyfree from ingredients injurious to the process or product produces aresult similar to that obtained -by the use of the alkali-metal saltsabove mentioned.

A The amount of alkali-metal compound required varies with the-nature ofthe phosphate; treated -and the temperature employed. Taking sodiumsulfate as an example, the addition of 10 to'20 per cent. is sufiicientto accelerate and complete the transformation of the phosphate tocitratesoluble condition By volatile constituents of alkali-metalcompounds we mean such part thereof as may be driven off by the actionof hot gases under the conditions herein described, leaving aresidue ofalkali-metal oxid, as for example, water, sulfur dioxid and oxygen,carbon dioxid, oxids of nitrogen, etc. By residual alkali we mean theresidue, consisting chiefly of alkali-metal oxid, remaining after theexpulsion of the volatile constituents of alkali metal compounds.

7 By increasing temperature we mean a temperature, of the .materialbelow that of fusion increasing from approximately 2000 degrees F. to2500 degrees F. By high temperature we mean a temperature below thefusin vided the gether in phate mixtures as of a steel eter and short len g point of the partially calcined material is not fused approximately2500 degrees F. understood that higher temperathe above are notinjurious proor balled tosuch manner as to interfere with thetransformation desired.

A suitable kiln for the treatment of cylinder of relatively largephosherein described consists diamgth as compared with the kilns used incement burning. For example,

a length eter of 8 dimensions.

is revolved b at, a speed per minu relatively con of from 30 to 50 feetand a to 10 feet diamare appropriate relative The kiln rests uponrollers and y power in the usual manner, of approximately 1 revolutionThe. inclination of the kiln is siderable, preferably f} inch to 1 inchper foot-of length. It will be understood, however, and increased ineffect on above figures that since increased the movement of the chargmay be varied conside The interior of the kiln is lined with a ofrefractory material, of fire-brick in'the u ment clinker or magne part.This lining is her of 1 preferably cons provided with a ow shelveslengthwise of the kiln, preferably begi at about upper end and extendone-fourth charge end of the kiln; the purpose of ridges is and thusterial to nally by to turn the the inner su speed clination produce asimilar e, the rably.

layer isting pper portion and cesite brick in the lower,

or ridges, extending nning the length from the ing nearly to thedisthese charge over and prevent it from sliding on rface,

to promote exposure of the ma intimate contact with the rapidly The kilnis heated a ame or flames or gas, and the heat so regulated that aerately high length of the interior. gases discharged from the lized inwell-known methods.

cooling the discharged of air and utilizing the port. combustion of thef with adv We cla 1. The

pulverizing natural phosphate of ing the with a ra temperature extendsthe interof coal-dust, oil

modentire The heat of the kiln may be utiboilers or for other purposes,by

antage. We

e process herein set Suitable devices for product by a current air soheated to supuel may be employed wish it to be undere do not limit ourina revolving kiln as forth y earried 'on in any type e in whlch therequired of hot gases process of making fertilizer by pid current of hotgases whil lime, phosphate with alkali-metal pound, an

mix-

com-

d calcining the mixture in contact e agi- .ing the phosphate With atincreasing temperature until the alkalimetal compound is substantiallydecomposed withevolution of volatile constituents, and finally at hightemperature until the phosphate becomes substantially citrate-soluble.

2. The process of making fertilizer by pulverizing natural phosphate oflime, mixing the phosphate with alkali-metal compound and calciningthemixture in contact with a rapid current, of hot gases while agitatingto present renewed surfaces to heat at increasing temperature until thealkali-metal compound is substantially decomposed with evolution ofvolatile constituents, and finally at high temperature until theresidual alkali is partly expelled and the phosphate becomessubstantially citrate-soluble.

3. The process of making fertilizer by pulverizing natural phosphate oflime, mixing the phosphate with alkali-metal compound and calcining themixture in contact with a current of hot gases of such velocity andtemperature that volatile constituents of the alkali-metal salt and partof the residual alkali shall be expelled and the material prevented fromfusing and kept in a porous condition, at increasing temperature andfinally at high temperature until the plhosphate becomes substantiallycitratesolu- :4.- The process of making fertilizer by pulverizingnatural phosphate of lime, mixalkali-metal compound and water, dryingthe mixture rapidly in such manner that it shall take a porous cellularform, and calcining the dried porous mixture in contact with a rapidcurrent of hot gases while agitating to present renewed surfaces toheat, at increasing temperatureland finally at high temperature untilthe phosphate becomes substantially citrate-soluble.

, 5. The process of making fertilizer pulverizing natural phosphate oflime, mixing the phosphate with alkali-metal compound and water, dryingthe mixture rapidly in such manner that it shall take a porous cellularform, porous mixture in contact with a rapid current of hot gases whil'cagitating to present renewed surfaces to heat, at increasing temperatureuntil the alkali-metal compound is substantially decomposed withevolution ofv volatile constituents and finally at high temperatureuntil the residual alkali is partly expelled and the phosphate becomessub stantially citrate-soluble.

6.' The process of making fertilizers by pulverizing natural phosphateof lime, mixing the phosphate with alkali-metal compound, preparing themixture in such'inanneras to give it a porous and open structure, freelypermeable by gases, and calcining the and calcining the dried prepa 'edInixture in eentact with a rapid Signedat SandhskjOhio, thisthirty-first current of hot gases, at increasing temperaday of October,1912.

ture until the alkalimetal compound is sub- A stantially decomposed withevolution of volv 3f atile constituents and finally at high tem-'perature until the residual alkali is partly Witnesses:

expelled and the phosphate becomes substan .HATTIE M. MEGGITT,

tially citrate -s0luble. I k ALLEN KUBACH.

